The invention relates to equipment for continuously feeding boxes or containers, which are initially stacked in a flattened tubular configuration in the form in which they are received from a paper products factory, to a packaging machine which is, for example, of the straight-line or other continuously operating type. The most similar prior art to the equipment described here is represented by the international patent application WO 1992/015450 entitled “Feeder mechanism for sleeve type cartons” and European patent EP 1 597 150 granted on May 14, 2008, entitled “Apparatus for forming containers”. The first of these patents describes equipment for feeding containers to the cellular conveyor of a packaging machine, in which the magazine holding the stacked containers is downwardly open and is located above the initial part of the cellular conveyor, with a carousel located between these two components and having a horizontal axis orthogonal to the direction of operation of the cellular conveyor, a plurality of suction cup pick-up units being mounted on the carousel in a radial arrangement with equal angular intervals between them, and being positioned in a way which is controlled by cams. The carousel rotates in phase with the conveyor of the packaging machine and moves each of its pick-up units in sequence in order to grip a container, draw it out of the base of the magazine, move it downwards, interact with an opening means, and, after a rotation of about 180°, insert the substantially open container at the correct time into a cell being formed in the initial part of the underlying conveyor, the container being supported by the wall opposite that with which the container touches the base of the cell. The equipment therefore requires extremely complicated, time-consuming, difficult and costly adjustments whenever the format of the containers is changed. It is also difficult to adjust the equipment in order to avoid damage to the container during its transfer to the conveyor of the packaging machine, each cell of which must always be positioned so that it is open at the rear and must then be closed on the container which has been fed into it. Furthermore, the height of this equipment is considerable, making it necessary to position the container magazine at a very high level, creating difficulties in the cyclic restocking and in the control of operation. However, the equipment is capable of operating continuously at high speed.
The equipment described in the second of the aforementioned patents partially overcomes the drawbacks of the first equipment, in that it enables the magazine to be positioned at a very low level and the containers are inserted into the cells of the packaging conveyor with their lower walls retained by the same means as those used to extract the containers from the feed magazine. The container feed means are therefore required to move between two “zero” reference positions, namely the base of the feed magazine and the base of the cells, which do not change when the format of the containers changes, and consequently the procedure for adapting the equipment to the changes in format is considerably simplified. In particular, the containers are drawn, one at a time, from the base of the magazine by a suction cup arm which initially swings downwards and then extends towards the initial part of the cellular conveyor of the packaging machine, where opening means operate at the correct time to open the container so that the latter can be inserted at the correct time into the cell which is open at the rear and which is being formed in the initial part of the conveyor. After the feed step, the suction cup arm releases the container, is lowered, is retracted under the magazine, and is then raised again to repeat the cycle which has been described. Clearly, equipment of this type has long periods of downtime and cannot operate at a speed as high as that of the carousel device described in the first of the cited patents. This equipment is subject to the same problems of adjustment as the first, for the purpose of avoiding damage to the container during its transfer to the conveyor of the packaging machine, each cell of which must always be positioned so that it is open at the rear and must then be closed on the container which has been fed into it.